The impact can be almost immediate. Figures show that once a patented drug goes head to head with a newer generic version, sales of the original quickly tumble by about 90pc as consumers switch to the cheaper alternative.

UK research group EvaluatePharma estimates that about $280bn (€215bn) of drug makers' revenue is under threat between 2012 and 2018 as treatments lose their patent protection.

But it also notes that while revenue from generic versions of drugs will continue to rise in that period to an annual $96bn, the figure will still only comprise about 11pc of a total $885bn in yearly prescription drug sales around the world.

With nine of the world's top 10 pharmaceutical firms having a manufacturing presence in Ireland – just AztraZeneca doesn't – there's been an understandable focus on the effect the 'patent cliff' could have on their Irish operations, and indeed the economy as a whole.

Recent preliminary data from the Central Statistics Office (CSO) showed that exports slumped 19pc in September to €7.3bn – with the pharmaceutical sector being blamed for a large part of the collapse. The CSO figures showed that industrial production in September fell by 12.7pc, with a 35pc decline in basic pharmaceuticals production.

The value of organic chemical exports fell by 33pc while there was a 10pc fall in exports of medical and pharmaceutical products.

Impacted

So, are things as rough as they look? Certainly, some major drug companies are going to be heavily impacted, but Davy stockbrokers' chief economist, Conall MacCoille, argues the potential negative impact to the fragile Irish economy may be overcooked.

In a report this week, he says that the importance of the pharmaceutical sector to Ireland may be "wildly overstated".

Sure, he says, the pharmaceutical and chemical sector accounted for 54pc, or €50bn, of the goods exported from these shores last year, or about a third of gross domestic product. But focusing on the export share of pharma "dramatically overstates" the importance of the import-intensive sector.

"Approximately one-third of export revenues from the pharmaceutical sector count towards Irish GDP," he says. "The remaining two-thirds are largely counted as imports of services, comprising licence and royalty fees by multinationals relating to intellectual property."

He maintains that any sharp decline in the value of Irish pharmaceutical exports will immediately lead to commensurate falls in services imports, limiting the impact on Irish GDP.

And while US patent expirations accelerate, Mr MacCoille also points out that patent expiration in other jurisdictions for particular drugs may not come about until years later in some cases. That in itself could smooth the impact on pharma firms' revenues.

But companies such as Pfizer, which makes cholesterol drug Lipitor, have already felt the whoosh of air from the patent cliff. The drug came off patent in 2011 and sales of the treatment tumbled.

Other blockbuster drugs made here include Eli Lilly's anti-depressant Cymbalta, which comes off patent next year and has annual sales of close to $5bn.

Takeda's Actos diabetes drug – also made in Ireland – had annual sales of $4.3bn in 2010 and came off patent in August. Amgen's arthritis treatment Embrel, which is also manufactured in Ireland and which had $3.3bn of global sales in 2010, comes off patent protection in 2016.

So even if the potential impact on Ireland's GDP may not be as severe as it's made out to be, the drug patent cliff could have a more immediate impact on company operations here. And for thousands of pharma workers, that must undoubtedly be food for thought.